Front Door Exterior Finish

Another thread on front-door finishes. No wood finish lasts forever in a tough exterior exposure. November 25, 2006

QuestionI am looking for recommendations on an exterior coating for a stain grade 2" thick cedar entry door that faces south. I need a clear topcoat with UV inhibitors and durability.

Forum Responses(Finishing Forum)
From contributor D:If you don't mind the fact that it's truly high gloss, in my opinion, automotive 2K acrylic urethane clear coat is the absolute nuts for this application. I've used it for years on wood with perfect results.

From the original questioner:Thanks. Automotive finishes are typically very hard. How does it do with wood movement? I'm concerned about cracks.
From contributor S:I think contributor D lives in Death Valley, as it is one of the few places on Earth where there are little or no changes in atmospheric humidity. The UK is like NW seaboard USA (I've been told) and we would always recommend an exterior woodstain for best performance. D-Dur will give good durability but maintenance will be a problem, as it will probably need stripping off before re-doing.
From contributor A:EM9300 Poly Carbonate Urethane from Target Coatings. Highly flexible single component waterborne. Great UV resistance, highly flexible and resistant to scratching and mild chemicals. That's what we use on all our exterior wood doors of fir, cedar, hemlock and fiberglass.
From contributor D:Not Death Valley, but close, in Phoenix, AZ. Prior to 1990, automotive clear coats were rather inflexible, but when urethane bumpers and plastic panels of every variety were introduced to cars, the formulations of clear coats changed to allow for the extreme flexibility of these plastic materials and since then, acrylic urethane clear coats have been able to be used with wood with no ill effects that I've been able to find. I know for a fact that they are much more flexible than conversion varnish. I painted a thin piece of balsa wood with both and the conversion cracked when flexed. The Rubber-Seal clear coat that I use didn't.
From contributor T:I have a similar dilemma. We are building a house (NE Wisconsin) that is facing the south with no roof over the front porch, so the door is fully exposed all year round. The owner wants a fiberglass door with gel stain and covered with a clear. I have talked to my coatings distributor and he is telling me that nothing will hold up more than 1 year and that I should paint the door instead. I don't want a call back here, so am getting ready to tell the buyer that I will not stain the door. Will the automotive finishes or the Target finishes described above really hold up for more than a year in this environment?
From contributor V:A fact of life for most any exterior door is that all exterior wood finishes fail, in time. How the finish fails and what is needed to recoat/replace/refinish the door then is important. In my estimation, it is not only the finish, but the long term that matters. While it is simple to get extreme barrier type finishes with great adhesion, what happens when the UV does finally cause it to fog, crack, lift or peel? Do you want to tell the owner that the door and frame and transom, etc, all need to be tented off for both chemical and mechanical removal and recoats? At about $2,000? Or more? After 30 years, and lots of experience like the above, I simply recommend Sikkens.
From Bob Niemeyer, forum technical advisor:2k urethanes for exterior wood will work just fine. They dry quicker than Sikkens products and have a "fine finish" look. As with any coating, things can happen to cause a failure. It seems people in the USA want a coating that requires no maintenance for years or decades. If you never wash your car, the paint will not last too long. Same rule goes for exterior finishes - if you want to keep them nice, a little maintenance along the way will add years. ICA's LP157 exterior urethane has been used for years with excellent results.
From the original questioner:I appreciate all the input. Bob, what kind of learning curve is there with this product?
From contributor A:I have gel stained and varnished hundreds of fiberglass doors and do about 20-50 in a year. Wash the door with lacquer thinners first. Old Masters gel stain works great. Let it dry for 24 hours and then topcoat with an exterior grade (preferably marine) varnish. The door should last for 2-4 years before it needs a light scuff and more varnish. After 6-10 years, expect to strip the outside and start the process over. As for cedar... I have cedar doors on my house and think that the super flexible waterborne urethanes are easy to use and look fantastic.
From contributor T:Things do happen to cause finish failure. Dust to dust. Not a bad recommendation in the bunch. The real question is: How much are you willing to do each year to maintain it and how much are you willing to do when it does fail to replace the finish?

Urethanes are great: very easy to no maintenance, but what a bugger to replace. Automotive finish would probably be very good too, if you cleaned the door regularly and waxed it once a year. I'm not sure what it would take to strip and replace it. Marine varnishes contain UV absorbers and/or free radical scavengers and mildew inhibiters, so they stand up well in exterior applications. They require a bit of maintenance every year or two and are not too bad to strip and replace when they do fail. I fall out on the side of "Willing to do a bit of maintenance if it will make replacement easier." One part Waterlox Marine, 1 part boiled linseed oil, 1 or 2 parts MS. Wipe on 3 or 4 coats. One new coat annually until it fails - then strip and recoat.

From contributor A:Stripping the gel stain and varnish off of a fiberglass door is very easy to do using a mild chemical stripper. Follow this with a wipe down of lacquer thinners and the door is ready to refinish. I've been experimenting using waterbornes on fiberglass doors as well, but have yet to come up with a system that I'm happy with..
From the original questioner:Does anyone else have experience with ICA exterior urethanes? What would be the expected life, facing south, high altitude in Colorado (cedar door)? When the coating does fail, is there a chemical stripper to remove it, or is it coming off with a belt sander?
From contributor V:I have sprayed lp157I for about three years. Works very well, quick dry, has a little bit of a learning curve, but what doesn't? The biggest problem with ICA is the lack of instruction to use product. The length of time finish will last is based on how many hours of direct sun it gets. It outlasts D-Dur and also SW auto urethane, which does come in matte finish. Sikkens has to be reapplied almost every year. If ICA or auto urethane has been outside for more than two years, it removes somewhat easily with meth choride strippers.

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